This invention relates to filter driers and more particularly to a bidirectional flow filter drier which is especially useful in heat pump systems or any other air conditioning or refrigerant systems where fluid flows may be reversed.
Bidirectional flow filter drier assemblies are well known in these fields and provide convenient, economical devices which utilize a common filter drier medium and a minimum of interconnections with the plumbing of the systems which is advantageous both from the standpoints of minimal original equipment and ease of maintenance and repair.
Two examples of prior art devices are shown in U.S. Pat. No. 4,125,469. In both of these examples, a plurality of check valves are arranged in a typical bridge circuit configuration to provide unidirectional fluid flow through a common filter drier unit, all of the components being housed in a common enclosure. In one example, four flapper valves are used to form the flow circuit while in the other example, each of the two duplicate valve assemblies is formed of a flapper valve and poppet valve combination.
Another example of prior art device is shown in U.S. Pat. No. 4,320,000 wherein four floating disc check valves are employed to provide unidirectional fluid flow through a molded desiccant core structure, also in a common enclosure.
Still another form of prior art device is shown in U.S. Pat. No. 4,177,145. In this unit, each valve assembly at either end of the common enclosure consists of an elastomeric or diaphragm type valve and spring-loaded ball, poppet type valve combination.
While these prior art devices are suitable for many purposes each of them is a fairly complex structure having a rather high number of components which introduce many assembly considerations and which increase the failure rate of the overall unit. Some of these devices require fairly difficult riveting or staking techniques or the placement of coil springs during assembly which adds to the complexity of the unit.
One of the objects of this invention is to provide a simplified and reliable biflow filter drier structure which utilizes a minimal number of components.
Another object of this invention is to provide valving structure which is easily fabricated from punched metal parts and readily assembled by spot welding technique.
Still another object of this invention is to provide an axial flow filter drier which utilizes a pair of identical check valve assemblies and a single molded desiccant core and in which the check valves are stainless steel reed type flapper valves formed from a single sheet of material.